I just placed my first bridge down too. I read a guide which stated that we won't be getting the chance to build another bridge for quite a while so it was important to make the first one count. It made me think real hard about how I was developing the island and placing houses...etc. Mine is somewhat in the middle of the island which connects the main landmass with the next largest.
so I placed my house above the resident services in a corner where two rivers crossed. Then a little north of my house, over the river, I placed Nook's Cranny. So I placed the bridge besides my 'garden' so I can easily run from my house/resident services to Nook's Cranny as that's where I'll be going the most.
So it's a sorta in the middle of the map.